Fluorescence of aromatic benzoxazole derivatives

Abstract

ketone in CC1«), and that they have been able to obtain a good fit for the observed variation by means of their calculations. We are grateful to Dr. Kaptein for providing us with a copy of his thesis, which represents a magnificent body of work.(25) Note Added in Proof. Fischer and Lehnig141* have determined the esr parameters of CI2CH• as g = 2.00829 ± 0.00010 and A = 16.79 ± 0.05 G. See H. Fischer and M. Lehnig, Phys. Chem., 75, 3410 1971); this paper reports the work cited in our ref 14a.search, The University of Georgia. The authors gratefully acknowledge illuminating conversations and correspondences with colleagues at the University of Georgia, especially G.

Novel fluorescent 2‐(2‐aminofluorophenyl)benzoxazoles: Syntheses and photophysical properties

“…It is noted that the excitation spectrum showed a correspondence between the blue emission and the long wavelength absorption. The shorter wavelength emission was observed in 3, and its fluorescence quantum yield was evaluated to be very small (Φ= 0.002 in methanol) [20], which is in sharp contrast to almost unity of 2-(4-aminophenyl)benzoxazole. The small fluorescence quantum yield of 3 is ascribed to the fluorine atoms substituted at the ortho-positions of 2-phenyl group [16].…”

Fluorescent behavior of 2‐(3,4,5,6‐tetrafluoro‐2‐hydroxyphenyl)imidazo‐[1,2‐a]pyridine in the presence of metal perchlorate

“…The chemical shifts are given in δ/ppm downfield from tetramethylsilane as an internal standard for 1 H nmr spectra and downfield from trifluoroacetic acid as an external standard for 19 F nmr spectra, respectively; J values are given in Hz. The fluorescence quantum yields were estimated relatively, on the basis of Φ f = 0.78 for 2-phenylbenzoxazole in cyclohexane [10].…”

Novel fluorescent quater‐ and quinquifurans: Syntheses and photophysical properties

“…We had already established that benzimidazolium groups as auxofluors on a fluorene gave a bright fluor, but with too short an emission wavelength [8]. It has long been known that benzoxazoles as auxofluors on oligophenylenes or fluorenes give fluors that are photostable, bright and fast (τ f = 1-2 nsec), albeit of far too short emission wavelength [9], so it seemed reasonable to prepare oligofurans terminated with benzoxazoles for this work. The placement of the strongly electron-attracting benzoxazol-2-yl group on the 2-and 5-positions of electron-releasing oligofurans was expected to give reasonably stable compounds.…”